As Hillary Clinton braces for a predicted presidential primary sweep by Barack Obama along the banks of the Potomac Tuesday night, her campaign reportedly is scrambling to comfort anxious donors and superdelegates who fear her campaign may be slipping out of her hands.

The Clinton campaign held a phone conference Monday aimed at rallying the troops, but some of those on the call said afterward that there is unease among Clinton’s supporters over what could become a big losing streak once Tuesday’s results in Virginia, Maryland and Washington D.C. are final, the New York Times reported.

“She has to win both Ohio and Texas comfortably, or she’s out,” an anonymous superdelegate who currently supports Clinton told the Times.

Those two states, as well as Rhode Island and Vermont, hold primaries on March 4.

Click here to read the FOX News Brainroom briefing book on the Potomac Primary to get the latest run down on Tuesday’s races.

Others said they’re now rethinking whether to support Clinton, saying they might “go with the flow” and support Barack Obama, if he continues to beat Clinton in the coming primaries.

Both the Clinton and Obama campaigns prepared to launch television ads in Ohio and Texas on Tuesday, and they added another debate to their schedule — Feb. 21 in Austin, Texas.

Meanwhile, Obama’s wave of momentum appears to be swelling — at least according to the polls.

New American Research Group surveys of 600 likely Democratic voters put Obama well ahead of Clinton in Maryland, where he leads 55 percent to 37 percent, and Virginia, where he leads 56 percent to 38 percent. Both leads are well beyond the polls’ 4-percent margin of error.

In the delegate race, 168 Democratic delegates are up for grabs in Tuesday’s primaries.

Among the Republicans, John McCain hopes to rebound with three wins Tuesday en route to his likely nomination. The Arizona senator lost contests in Kansas and Louisiana during the weekend, but managed a narrow win in Washington state caucuses that Mike Huckabee is now challenging.

There are 116 delegates on the table for Republicans Tuesday night.

An Associated Press tally shows Clinton currently holding a slim lead among delegates - 1,147, compared to 1,124 for Obama. But Clinton’s lead relies on unpledged “superdelegates,” who are not bound by the voters’ mandate in state nomination contests. An initial tabulation of the total popular vote showed Obama likely to pull ahead once the results of states that held caucuses are fully counted.

The latest national polls show Clinton’s lead among the states sliding to razor-thin margins, and in some cases, she is ceding the lead to Obama. Over the last 10 days, RealClearPolitics tracking average of recent polls shows Clinton still leading Obama 45.3 percent to 43.7 percent.

But two recent polls put Obama ahead in the national chase, including a Feb. 8-9 USAToday/Gallup poll that put Obama ahead by 3 percentage points — 47 percent to 44 percent — among 525 Democrats and Democrat leaners. (+/- 5 percent)

And a new USAToday/Gallup poll shows Obama faring better than Clinton against McCain, who has all but wrapped up the Republican nomination. The Feb. 8-10 poll shows Obama leading the Arizona senator by 4 percentage points, whereas Clinton trails the Arizona senator by 1 percentage point. Both results are within the poll’s margin of error, meaning the races are statistically tied.

In hypothetical general election match-ups, a new AP poll conducted after last week’s Super Tuesday contests found Obama edging McCain, 48 percent to 42 percent, while Clinton and the Arizona senator were statistically tied — 46 percent for Clinton to 45 percent for McCain.

Obama was traveling late Tuesday to Wisconsin, which votes next week, along with Hawaii, where the Illinois senator grew up.

With the Clinton campaign all but conceding losses Tuesday, as well as in other primaries during the month, the New York senator prepared to fly to Texas.

“I wouldn’t be doing this if I didn’t think I would be the best candidate,” Clinton told reporters Monday as she campaigned near Baltimore. “So I’m going forward — every day, we get to make our case to the American people.”

Despite what the poll numbers suggest, Clinton’s strategists argued that she would be the stronger competitor against McCain because she has stared down Republicans throughout her career in politics and public service.

Clinton “has withstood the full brunt of this kind of attack and will be able to neutralize what is likely to happen particularly with a nominee who is not as well known,” said Clinton strategist Mark Penn

“In a general election the Republicans would spring into action and quickly, if he were the nominee, roll out his full record,” Penn said of Obama.

The Associated Press contributed to this report.